Gender-specific social experiences and the development of aggressive and sexual behavior in male mice

This study examined influences of gender-specific social experiences on the development of aggressive and sexual behavior in male mice. To determine the effects of gender-specific social experience three different types of groups were constituted after the animals had been weaned. The subjects were randomly assigned to different treatments. Female groups were composed of one experimental male and three female cohabitants. Male groups were composed of five experimental males each, and the mixed-sex groups were composed of two experimental males and of two females. The experimental subjects stayed in these groups until the age of approximately three months, when the testing for sexual and aggressive behavior commenced. For the sexuality tests, a receptive female was placed in the home cage of the experimental male for ten minutes. A nonaggressive male was placed in the home cage of the experimental male for seven minutes for the aggression tests. The experimental males were administered both sexuality and aggression tests, the sequence of testing sexual and aggressive behavior was systematically varied in order to control the influence of the two different types of behavioral tests. The results showed that males with only male social experiences showed fewer responses and were less active in both the aggression and sexuality tests than the males from the two other types of groups. Significant positive correlations between activity during aggression and sexual tests were obtained for all three groups. © 1994 Wiley-Liss, Inc.     

The effects of sex-role taking on children's responses to aggressive conflict situations

The effects of sex-role taking on children's responses to aggressive conflict situations were investigated in the present study. Subjects were 40 boys and girls aged 8–9, who were asked to take the role of boy and girl story characters involved in the following kinds of aggressive situations: victim of a verbal attack, victim of a physical attack, and witness to an attack upon a friend. A significant interaction effect between type of conflict situation and sex of story character was obtained. Subjects expected boy characters to retaliate more strongly than girl characters when intervening in an attack upon a friend, and girl characters to retaliate more strongly than boy characters when being verbally or physically assaulted. These findings suggest the importance of situational factors in determining children's sex-stereotyped expectations for aggressive retaliation.     

The effects of gormone manipulations on aggressive target-biting in mice

Aggressive biting of an inanimate target by mice was studied. Males attacked the bite-target more frequently than females, but this difference disappeared after castration when the response rate of the males approached that of the females. Ovariectomizing the females had little effect on their bite-attack frequencies. Subsequent androgen injections restored the biting-attack frequency of the castrated males to preoperative levels but had little effect on the intact males. Estrogen had little effect on the response frequency of the females, whereas androgen produced a slight increase in their bite-attack frequency. Results indicate that androgen is critical for the maintenance of this aggressive response and that the single subject paradigm utilized in this study was a sensitive measure of aggressive tendencies in mice.     

The effects of urine on aggressive responses by male golden hamsters

Twenty adult male golden hamsters were isolated into individual cages for a period of six weeks, at the end of which time they had introduced into their home cages, on three occasions, a castrated male intruder. On each occasion the castrated intruder was daubed on the anogenital region with urine from one of three sources: (1) intact females, (2) other castrated males, and (3) intact males. Urine from a different source was applied to the castrated intruder on each of the three tests. Resident males consistently showed more aggression, sniffing, and following and less defensive behavior than the intruders. However, aggression by the resident males showed a significant variance over the three urine treatments given to the intruder. It is concluded that like male mouse urine, male hamster urine contains attack-provoking cues, but that unlike that of the mouse, female urine does not appear to be attack-inhibiting in this species.     

Sex differences in aggressive behaviour in various strains of mice

Two nonalbino inbred (C57 BL/6 and C3H/He) and one albino strain (Swiss) of mice were compared for female aggression toward intruders: 1 in period of lactation, 2 in nonlactating state and (3) in nonlactating state but previously rubbed with urine of lactating females; and for male aggression toward familiar or unfamiliar opponents. The results showed that resident females of the C57 and Swiss strain vigorously attack lactating intruders introduced into their cages. This effect was mediated by urinary cues emitted by the latter mice. It was also shown that Swiss residents displayed aggression towards nonlactating females, irrespective of their strain. Groups of C57 residents reacted most aggressively towards Swiss females, less aggressively towards C3H intruders, but did not show any aggression towards their own nonlactating conspecifics. In contrast, none of the C3H resident female groups displayed aggression towards intruding females of any category or strain. The results also showed that the males of the three strains displayed little (Swiss and C3H) or no aggression (C57) towards familiar opponents, whereas they directed increased aggressive responses towards unfamiliar ones. Comparisons among the three strains of mice revealed that Swiss males were the most aggressive in either situation. On the other hand, the finding that C3H males showed aggressive responses suggested that male and female aggression are, in this strain, under separate genetic or hormonal control.     

Effects of early exposure to mating on adult sexual behavior in male mice varying in their genetic disposition for aggressive behavior

This study examined whether the sexual behavior of adult male mice is influenced by exposure in early postnatal life to brief episodes of mating. Another focus of interest was the interplay between a genetic disposition for aggressive behavior and the early exposure experiences. The subjects used in the study were male mice of the fiftysixth generation of selection for high (Turku aggressive, TA) and low (Turku non-aggressive, TNA) levels of aggressiveness. Moderately aggressive males of the parental strain (normal, N) were also used. Subjects of each strain were exposed from 21 to 32 days of age to mating mice behind a wire mesh screen. Control subjects were placed in a comparable enclosure, but were exposed to nothing. The results showed that male mice exposed to mating early in life showed a higher rate of activities in the sexuality tests, including aggressive responses. A genetic potential for aggressive behavior was related to a higher degree of sexual activity, and the early exposures optimized the hereditary attributes. The relation between sexual and aggressive behavior is discussed. © 1994 Wiley-Liss, Inc.     

Effects of cohabitation with another female on aggressive behaviour in pregnant mice

Pregnant, nonpregnant (but mated) and virgin females were individually housed or lived with a pregnant or nonpregnant cagemate. They were subjected to a series of successive daily encounters with a male intruder, the cagemate being excluded. The most aggressive subjects were pregnant females living with a pregnant cagemate. Isolated pregnant females were as aggressive as pregnant females with a nonpregnant cagemate. Nonpregnant and virgin females were the least aggressive. Nevertheless nonpregnant subjects living with a pregnant cagemate generated higher aggressive scores than nonpregnant females living alone. The way in which a pregnant cagemate influences the aggressive behaviour of another pregnant or nonpregnant female is discussed.     

Effects of alpha and beta adrenergic antagonists on aggressive behavior in male mice

The effects of a variety of alpha and beta adrenergic antagonists were examined on the social encounters of isolated male mice with anosmic male partners. A range of alpha antagonists, including phentolamine, prazosin, and yohimbine, all suppressed social aggression. A range of beta antagonists, including propranolol, atenolol, metaprolol, and ICI 118, 551, also reduced this type of attack. Ethological assessment of the lowest effective dose of these adrenergic antagonists revealed a marked inhibitor action on offensive, social, and nonsocial behavior, while defensive responses and immobility were enhanced. It is concluded that the noradrenergic system has a significant non-specific role in mediating intermale aggression via both alpha and beta adrenergic receptor subtypes. © 1993 Wiley-Liss, Inc.     

Isolation-induced facilitation of male sexual behavior in mice

Sexual performance of male mice housed individually or in groups of 3 or 12 was compared. Experiment 1 examined naive males presented at weekly intervals with ovariectomized, estrogen-primed, progesterone-treated females. Performance in isolates was consistently superior and reached an asymptote that was twice that of grouped animals. Reversal of housing conditions reversed performance. Experiment 2 varied intervals of isolation among subjects, finding facilitation at several intervals. Experiment 3 compared animals under different population densities. Density did not alter the effects of isolation and grouping. In all experiments, additional tests with target males indicated that aggressive and sexual performance were moderately correlated and responded similarly to parametric manipulations. These results parallel and extend studies of isolation-induced aggression.     

The ventromedial hypothalamus and aggressive behaviour in rats

Male rats were given bilateral lesions in either the anterior or posterior ventromedial hypothalamus (VMH). The intermale aggressive behaviour of these animals within their own territory was observed before and after the surgical procedure and compared with the behaviour of sham-operated animals. The effects of anterior VMH lesions include an increased tendency to respond with frontal threatening upon approach of a conspecific male. This behaviour closely resembles the aggressive responses described in “shock-induced aggression” tests. Posterior VMH lesions facilitate territorial aggressive behaviour characterized by approaching the opponent followed by lateral threatening and fighting. It is suggested that 2 distinct neural substrates exist, which serve to inhibit defensive (anterior-VMH) and offensive (posterior-VMH) intermale aggression, respectively.     

Relationship between sexual activity and intraspecific fighting in male mice

Significantly more male mice having cohabited and mated with intact females subsequently displayed intraspecific fighting behavior after castration than males having cohabited with noncycling (ovariectomized) females. Also, intact males that failed to achieve a criterion for aggression during three screening tests subsequently showed a marked increase in fighting after having had copulatory experience relative to males that lived with ovariectomized females. Lastly, spontaneously aggressive males copulated more frequently than nonfighters.     

Maternal stress and pituitary-adrenal manipulations during pregnancy in rats: effects on morphology and sexual behavior of male offspring.

The purpose of the present study was to determine whether the demasculinizing and feminizing effects of prenatal stress (i.e., stress applied to the mother during pregnancy) in rats reported previously are mediated by activation of the maternal pituitary-adrenal axis. Neither whole-body restraint, with or without hyperthermia, nor ACTH treatment during the last third of gestation had any reliable effect on masculine or feminine sexual behavior in male Sprague-Dawley offspring, although these treatments produced maternal pathology and evidence of maternal adrenocorticoid release. Significant littermate similarity was found for almost every morphological and behavioral measure. Failure to control for the litter variable may account for many previously reported effects of prenatal stress on sexual behavior in rats. The discrepancy between the present and earlier findings is discussed in terms of methodological and theoretical considerations.     

The judgement of behaviour as aggressive and sanctionable

The influence of the factors norm deviation, intent, and injury, on the judgement of a critical act as aggressive and sanctionable was tested using a 2 × 2 × 2 factorial design. Scenarios depicting aggressive interactions represented the experimental conditions. 859 school children rated these scenarios on bipolar rating scales. The results show that norm deviation, intent, and injury, are important criteria for the interpretation of aggressive behaviour. Judging an action as sanctionable proved to be more sensitive for the variation of factors than the interpretation of behaviour as aggressive. In addition, an analysis of how the scenarios representing the experimental conditions were subjectively interpreted by the subjects was carried out. This showed that all combinations of the three definition criteria are psychologically meaningful. However, preferences were observed for specific interpretation patterns.     

The effects of phencyclidine and chlordiazepoxide on target biting of confined male mice

Target-biting of confined mice increases following delivery of tail shock and decreases during a tone that precedes the shock. Both phencyclidine and chlordiazepoxide reduced biting (dose dependently) following shock and had no effect on biting during the tone. These observations are discussed in reference to previous reports, which infer that the effects of phencyclidine and chlordiazepoxide on aggression might depend upon the baseline rate of the behavior.     

Chronic effects of high salt intake and conflict stress on blood pressure in primates

The effects of combined behavioral stress and high dietary salt on blood pressure were examined in baboons (N=4) over the course of 1 year. Either high salt diet (240 mEq Na⁺/day) or conflict stress were administered for 8 to 16 weeks, followed by high salt intake and stress combined. Mean arterial pressure (MAP) increased by 8 mmHg during high dietary salt alone, by 4 mmHg during stress alone, and increased further to 14 mmHg above baseline during combined salt and stress. Control baboons (N=2) had no change in MAP across 47 weeks. The data indicate additive effects of chronic high dietary salt intake and behavioral stress on blood pressure in non-human primates.     

Children's aggressive behaviour and teacher–child conflict in kindergarten: Is teacher perceived control over child behaviour a mediating variable/

Background Research repeatedly showed young children's aggressive behaviour to predict relationship difficulties with the teacher. Aims To examine a possible mediating variable in this process and in the stability of relationship difficulties across the school year, namely teacher perceived control over child behaviour. Sample The sample consisted of 139 Belgian kindergartners and their teachers. Method Data were collected throughout kindergarten at three measurement occasions: children's aggressive behaviour was measured by means of a peer nomination procedure during the first trimester, teacher perceived control over child behaviour was assessed by means of a teacher questionnaire during the second trimester, and teacher–child conflict was measured by means of a teacher questionnaire during the first and third trimesters. Correlations among all study variables were calculated and different models were estimated and compared by means of structural equation modelling. Results Teacher perceived control completely mediated the relationship between aggressive behaviour and teacher–child conflict (after controlling for the concurrent association between aggressive behaviour and conflict, and the stability of conflict). In addition, teacher perceived control accounted for part of the stability in conflict across the school year. Conclusions Teacher perceived control over child behaviour has been found to act as a mediating mechanism between child aggressive behaviour and teacher–child conflict at the beginning of kindergarten and teacher–child conflict at the end of the year.